(Important Questions) Chemistry : Important Questions For CBSE Class XII ( Haloalkanes and Haloarenes) : Part - 3

Chemistry : Important Questions For CBSE Class XII ( Haloalkanes and Haloarenes) : Part - 3

(Q.101) In the Grove’s process, chloroalkanes are prepared by passing HCl gas through a suitable alcohol in the presence of anhydrous zinc chloride. The purpose of using zinc chloride is ( 1 mark )
(a) to help in the cleavage of C-C bond.
(b) to help in the cleavage of C-H bond.
(c) to help in the cleavage of C-O bond.
(d) to provide the reaction with moisture free conditions.

(Q.102) The chlorobenzene is commercially prepared by Raschig’s process in which a mixture of benzene vapours, air and hydrogen chloride is passed over heated ( 1 mark )
(a) Copper powder.
(b) Cuprous chloride.
(c) Cupric chloride.
(d) Alumina.

(Q.103) Bromoalkanes are obtained by refluxing a suitable alcohol with constant boiling hydrobromic acid in the presence of conc. H2SO4 as catalyst. The constant boiling HBr has aqueous composition of ( 1 mark )
(a) 48%.
(b) 58%.
(c) 68%.
(d) 78%.

(Q.104) Iodoform was earlier used as an antiseptic for dressing wounds, its antiseptic properties are due to liberation of a substance when iodoform comes in contact with skin, the substance is ( 1 mark )
(a) Phosgene.
(b) Iodine.
(c) Chlorine.
(d) Hydrogen iodide.

(Q.105) The addition of hydrogen halides to an unsymmetrical alkenes takes place according to ( 1 mark )
(a) SN1 mechanism.
(b) SN2 mechanism.
(c) Markownikoff’s Rule.
(d) Saytzeff’s Rule.

(Q.106) The alkyl halide that depletes the ozone layer significantly is ( 1 mark )
(a) Monochloromethane.
(b) Dichloromethane.
(c) Trichloromethane.
(d) Tetrachloromethane.

(Q.107) For the same alkyl group, the boiling points of haloalkanes decreases in the order ( 1 mark )
(a) RF>RCl>RBr>RI.
(b) RCl>RBr>RI>RF.
(c) RBr>RI>RF>RCl.
(d) RI>RBr>RCl>RF.

(Q.108) Most widely used refrigerant freon (freon-12) is prepared by ( 1 mark )
(a) Etard’s reaction.
(b) Swarts reaction.
(c) Finkelstein reaction.
(d) Birnbaum-Simonini reaction.

(Q.109) Cinnamyl chloride is ( 1 mark )
(a) 3-Chloro-1-phenylprop-1-ene.
(b) 2-Chloro-1-phenylprop-2-ene.
(c) 1-Chloro-3-phenylprop-1-ene.
(d) 2-Chloro-3-phenylprop-2-ene.

(Q.110) DDT was first prepared in 1873 but it was not until 1939 that Paul Muller at Geigy pharmaceuticals in Switzerland, discovered the effectiveness of DDT as an insecticide, he was awarded Noble Prize for this discovery in 1948 in subject ( 1 mark )
(a) Chemistry.
(b) Medicines and Physiology.
(c) Biochemistry.
(d) Pharmaceuticals.

(Q.111) The DDT is prepared by heating chlorobenzene with chloral in the presence of conc. H2SO4, the chloral is ( 1 mark )
(a) Trichloroacetaldehyde.
(b) Dichloroacetaldehyde.
(c) Trichloroacetone.
(d) Dichloroacetone.

(Q.112) The markownikoff’s rule reverses in the presence of peroxide, but this is possible only in case of ( 1 mark )
(a) HI.
(b) HBr.
(c) HCl.
(d) HF.

(Q.113) Dehydrohalogenation or elimination reactions of alkyl halides having strongly acidic ?-hydrogen takes place through ( 1 mark )
(a) E1 mechanism.
(b) E2 mechanism.
(c) E1cB mechanism.
(d) Benzyne mechanism.

(Q.114) The nucleophilicity order of different halide ions is as ( 1 mark )
(a) I->Br->Cl->F-.
(b) Br->Cl->F->I-.
(c) Cl->F->I->Br-.
(d) F->I->Br->Cl-.

(Q.115) When chlorobenzene is treated with NaNH2 in liquid ammonia at 196K, aniline is formed. This reaction takes place by ( 1 mark )
(a) E1 mechanism.
(b) E2 mechanism.
(c) E1cB mechanism.
(d) Benzyne mechanism.

(Q.116) During the preparation of iodoalkanes a suitable alcohol is refluxed with constant boiling hydriodic acid (57%). HI may also be prepared in situ by the action of ( 1 mark )
(a) Phosphoric acid on KI.
(b) Sulphuric acid on KI.
(c) Phosphoric acid on KIO3.
(d) Sulphuric acid on KIO3.

(Q.117) A copper strip is heated strongly in Bunsen flame till it ceases to impart any greenish or bluish flame, then a pinch of organic halide is placed on this hot strip and reintroduced into the flame, if a green or bluish green flame reappears it indicates the presence of halogen but does not confirm the nature of halogen. This test is ( 1 mark )
(a) Lassaigne’s test.
(b) Mollisch’s test.
(c) Victor Mayer test.
(d) Beilstein test.

(Q.118) Williamson’s synthesis is a nucleophilic substitution reaction of alkyl halides which results in the formation of ( 1 mark )
(a) Esters.
(b) Ethers.
(c) Amides.
(d) Acid anhydrides.

(Q.119) The incorrect statement about DDT is ( 1 mark )
(a) The problems related to extensive use of DDT began to appear in early 1970s.
(b) Many species of insects developed resistance to DDT and it was also discovered to have high toxicity towards fish.
(c) The chemical stability of DDT and its fat solubility further increased the problems.
(d) DDT is not completely biodegradable and gets deposited in fatty tissues, its use has been banned in USA since 1973.

(Q.120) The allylic bromination can be carried out with the help of ( 1 mark )
(a) N-bromosuccinic acid.
(b) N-bromosalicylic acid.
(c) N-bromosalicylamide.
(d) N-bromosuccinimide.

(Q.121) If in lassaigne’s test, AgNO3 reacts with lassaigne’s extract to give white ppt that are soluble in NH4OH, it indicates the presence of ( 1 mark )
(a) Fluorine.
(b) Chlorine.
(c) Bromine.
(d) Iodine.

(Q.122) The nucleophilic substitution of halide group with isocyanide group can be affected by reacting alky halide with ( 1 mark )
(a) NaCN.
(b) KCN.
(c) AgCN.
(d) LiCN.

(Q.123) Quantitative estimation of active hydrogens in an organic compound can be done by ( 1 mark )
(a) Lassaigne’s method.
(b) Mollisch’s method.
(c) Victor Mayer method.
(d) Zerewitnoff’s method.

(Q.124) Benzal chloride is ( 1 mark )
(a) 1,2-Dichloro-1-phenylethane.
(b) 1,1-Dichloro-1-phenylmethane.
(c) 1,1-Dichloro-2-phenylethane.
(d) 1,1,1-Trichloro-1-phenylmethane.

(Q.125) Aryl chlorides can also prepare Grignard reagents but solvent used instead of ether (used for alkyl chlorides) is ( 1 mark )
(a) Pyridine.
(b) Methanol.
(c) Ethanol.
(d) Tetrahydrofuran.

(Q.126) Walden inversion takes place in ( 1 mark )
(a) Free radical mechanisms.
(b) Electrophilic mechanisms.
(c) SN1 mechanisms.
(d) SN2 mechanisms.

(Q.127) Preparation of alkyl fluorides by heating suitable chloro or bromoalkanes with inorganic fluorides such as AsF3, SbF3, CoF3, AgF, Hg2F2 etc. is known as ( 1 mark )
(a) Etard’s reaction.
(b) Swarts reaction.
(c) Mendius reaction.
(d) Birnbaum-Simonini reaction.

(Q.128) Halogenation of alkanes that is reversible is ( 1 mark )
(a) Fluorination.
(b) Chlorination.
(c) Bromination.
(d) Iodination.

(Q.129) The dehydrohelogenation of haloalkanes results in the formation of ( 1 mark )
(a) an alkane.
(b) an alkene.
(c) an alkyne.
(d) an aromatic hydrocarbon.

(Q.130) The optimum temperature for allylic halogenation of alkenes is ( 1 mark )
(a) 473K.
(b) 573K.
(c) 673K.
(d) 773K.

(Q.131) The most convenient method for the preparation of haloalkanes involves the substitution of –OH group of an alcohol by the halogen atom. For a given alcohol, the reactivity of halogen acids decreases in the order ( 1 mark )
(a) HCl>HBr>HI.
(b) HBr>HI>HCl.
(c) HI>HCl>HBr.
(d) HI>HBr>HCl.

(Q.132) PBr3 and PI3 used for the preparation of alkyl halides from alcohols, are not very stable compounds, these are generally prepared in situ by the action of a substance on bromine and iodine respectively, the substance is ( 1 mark )
(a) Red phosphorous.
(b) White phosphorous.
(c) Potassium iodide.
(d) Silver iodide.

(Q.133) If the structure of alkyl halide during dehydrohalogenation reaction is such that it can undergo H-elimination from two different sites, then the more highly substituted alkene is the major product. This generalization is known as ( 1 mark )
(a) Markownikoff’s Rule.
(b) Saytzeff’s Rule.
(c) Kharasch’s effect.
(d) Racemization.

(Q.134) Side chain-halogenation of haloarenes is a reaction having ( 1 mark )
(a) SN1 mechanism.
(b) SN2 mechanism.
(c) Free radical mechanism.
(d) Benzyne mechanism.

(Q.135) The iodoalkanes can be prepared from corresponding chloro or bromoalkanes by heating with NaI in acetone or methanol, this reaction is called as ( 1 mark )
(a) Etard’s reaction.
(b) Swarts reaction.
(c) Finkelstein reaction.
(d) Birnbaum-Simonini reaction.

(Q.136) The sandmeyar reaction is modified to gattermann reaction by using a mixture of freshly prepared copper powder in the presence of halogen acid instead of cuprous halide dissolved in corresponding halogen acid (sandmeyer reaction), the yield of gattermann reaction is around ( 1 mark )
(a) 40%.
(b) 60%.
(c) 80%.
(d) 90%.

(Q.137) Victor Grignard discovered Grignard reagents (RMgX) in1900, for this discovery, he was awarded Noble Prize in chemistry in ( 1 mark )
(a) 1902.
(b) 1912.
(c) 1922.
(d) 1932.

(Q.138) Alkyl halides are converted into ethers by Williamson’s synthesis, another way to convert alkyl halides into ethers is by using ( 1 mark )
(a) Silver hydroxide.
(b) Sodium hydroxide.
(c) Dry silver oxide.
(d) Sodium peroxide.

(Q.139) For the nucleophilic substitution of –OH group by halide ion during the preparation of haloalkanes from alcohols, the reactivity order of different alcohols is ( 1 mark )
(a) tertiary>secondary>primary.
(b) secondary>primary>tertiary.
(c) primary>tertiary>secondary.
(d) tertiary>primary>secondary.

(Q.140) When the aqueous ethanolic solution of a haloalkane (particularly iodoalkanes) is heated with silver cyanide, the chief product formed is ( 1 mark )
(a) Alkyl cyanides.
(b) Alkyl isocyanides.
(c) Alkyl cyanates.
(d) Alkyl isocyanates.

(Q.141) Due to prevailing basic conditions of the reaction, the Wurtz reaction is not responded by ( 1 mark )
(a) Tertiary alkyl halides.
(b) Secondary alkyl halides.
(c) Primary alkyl halides.
(d) Sodium metal.

(Q.142) In Borodine-Hunsdiecker reaction, bromoalkanes are prepared by refluxing the silver salt of a fatty acid with bromine in ( 1 mark )
(a) Ethanol.
(b) Acetone.
(c) Diethyl ether.
(d) Carbon tetrachloride.

(Q.143) Tetraethyl lead (TEL) is an important antiknocking agent in gasoline used for running vehicles, it is prepared by reacting alkyl halide with an alloy of lead in the presence of dry ether, the alloy of lead is ( 1 mark )
(a) Li-Pb.
(b) Na-Pb.
(c) Hg-Pb.
(d) Zn-Pb.

(Q.144) The incorrect explanation to the low reactivity of aryl halides in comparison to that of alkyl halides is ( 1 mark )
(a) Resonance effect.
(b) Difference in hybridization of carbon atoms in C-X bond.
(c) Polarity of C-X bond.
(d) +I effect of benzene ring.

(Q.145) The silver salts of carboxylic acids on refluxing with I2 dissolved in CCl4 gives esters of carboxylic acid instead of iodoalkanes. This reaction is known as ( 1 mark )
(a) Etard’s reaction.
(b) Swarts reaction.
(c) Finkelstein reaction.
(d) Birnbaum-Simonini reaction.

(Q.146) The Dow’s process is used for the preparation of ( 1 mark )
(a) Chlorobenzene.
(b) Fluorobenzene.
(c) Bromobenzene.
(d) Phenol.

(Q.147) Organohalogen compound amongst the following that is used as an anaesthetic agent is ( 1 mark )
(a) Chloramphenicol.
(b) Chloroquine.
(c) Chloromycetin.
(d) Halothane.

(Q.148) Picric acid is ( 1 mark )
(a) 2,4,6-Trinitrotoluene
(b) 2,4,6-Trinitroaniline.
(c) 2,4,6-Trinitrophenol.
(d) 1,3,5-Trinitrobenzene.

(Q.149) The benzene diazonium chloride needed for the sandmeyer reaction to produce aromatic halides is produced by diazotisation reaction that takes place at ( 1 mark )
(a) 0-50C.
(b) 5-100C.
(c) 10-150C.
(d) 15-200C.

(Q.150) The metallic powder that is used in Ullmann synthesis of diphenyl is ( 1 mark )
(a) Manganese powder.
(b) Chromium powder.
(c) Magnesium powder.
(d) Copper powder.

(Q.151) When phosphorous trihalide is reacted with a suitable alcohol to form haloalkane, the side product of reaction is ( 1 mark )
(a) Hypophosphorous acid.
(b) Phosphorous acid.
(c) Phosphoric acid.
(d) Pyrophosphoric acid.

(Q.152) The reaction amongst the following that does not involve the use of aryl halides is ( 1 mark )
(a) Wurtz reaction.
(b) Wurtz-Fittig reaction.
(c) Fittig reaction.
(d) Ullmann reaction.

(Q.153) The allylic chlorination is generally done with chlorine at 773K, but it can also be carried out at lower temperature with the help of ( 1 mark )
(a) CuCl/HCl.
(b) Cu/HCl.
(c) HCl.
(d) SO2Cl2.

(Q.154) The chlorobenzene can be converted into benzene by reduction with nascent hydrogen produced by an alloy(metallic) in the presence of alkali, the metallic alloy used is ( 1 mark )
(a) Cd-Al.
(b) Ni-Cd.
(c) Hg-Cd.
(d) Ni-Al.

(Q.155) The thionyl chloride method is preferred over hydrogen chloride or phosphorous chloride method for the preparation of haloalkanes because both the by-products (SO2 and HCl) in this case are gases and escape leaving behind pure chloroalkane. This reaction takes place in the presence of ( 1 mark )
(a) Conc. sulphuric acid.
(b) Phosphoric acid.
(c) Anhydrous zinc chloride.
(d) Pyridine.

(Q.156) The poisonous gas phosgene is chemically ( 1 mark )
(a) Thionyl chloride.
(b) Carbonyl chloride.
(c) Sulphonyl chloride.
(d) Sulphuryl chloride.

(Q.157) The fluoroarenes are prepared by heating the corresponding diazonium tetrafluoroborates that are in turn obtained by diazotisation of suitable primary amine with aqueous NaNO2 in the presence of fluoroboric acid (HBF4) at 273-278K. This reaction is known as ( 1 mark )
(a) Balz-Schiemann reaction.
(b) Swarts reaction.
(c) Finkelstein reaction.
(d) Birnbaum-Simonini reaction.

(Q.158) The optimum temperature required for the Riemer-Tiemann reaction is ( 1 mark )
(a) 240K.
(b) 340K
(c) 440K
(d) 540K

(Q.159) The substance that is added to destroy traces of phosgene formed by aerial oxidation of chloroform on prolonged storage is ( 1 mark )
(a) Ether.
(b) Ester.
(c) Alcohol.
(d) Carboxylic acid.

(Q.160) The reaction of haloalkanes with aqueous sodium or potassium hydroxide or moist silver oxide to produce alcohols is an example ( 1 mark )
(a) Elimination reaction.
(b) Dehalogenation reaction.
(c) Reduction reaction.
(d) Hydrolysis reaction.

(Q.161) The hydride ion transfer takes place at each step in the reduction done by using ( 1 mark )
(a) H2 in the presence of Nickel.
(b) Sodium in the presence of ethanol.
(c) LiAlH4.
(d) Zn and NH4OH.

(Q.162) Grignard reagents (RMgX) are potential sources of carbanions because of ( 1 mark )
(a) polar C-Mg bond.
(b) +I effect of alkyl group.
(c) solvent properties of ether with which it is stored.
(d) their ability of react in any medium.

(Q.163) The maximum dipole moment amongst the different halomethanes is that of ( 1 mark )
(a) CH3F.
(b) CH3Cl.
(c) CH3Br.
(d) CH3I.

(Q.164) Refluxing is ( 1 mark )
(a) Continuous heating of a liquid at isothermal conditions.
(b) Adiabatic heating of liquid in an isolated system.
(c) Adiabatic heating of liquid in an isolated system.
(d) The process of heating a liquid in a flask with a condenser so that the vapours are condensed back into the same flask.

(Q.165) Alkyl halide with Garlic like odour is ( 1 mark )
(a) vinyl chloride.
(b) methyl iodide.
(c) benzyl iodide.
(d) allyl iodide.

(Q.166) Westron is a highly toxic halogen derivative liquid used as fumigant and insecticide formed the reaction of acetylene with the halogen that is ( 1 mark )
(a) Fluorine.
(b) Chlorine.
(c) Bromine.
(d) Iodine.

(Q.167) Teflon is a white, dense, highly crystalline, extremely inert compound. Chemically it is ( 1 mark )
(a) poly monochlorotrifuoroethylene.
(b) poly monofluorotrichloroethylene.
(c) poly tetrafluoroethylene.
(d) poly tetrachloroethylene.

(Q.168) The fluorinating agent generally used for the preparation of Freon-12 is ( 1 mark )
(a) MgF2.
(b) WF3.
(c) TiF4.
(d) SbF5.

(Q.169) A hydrocarbon C5H10 does not react with chlorine but gives a single monochloro compound, C5H9Cl in bright sunlight. Identify the hydrocarbon. ( 2 Marks )

(Q.170) Identify isomers are possible monochloro structural isomers that would be expected to form on free radical chlorination of
(CH3)2CHCH2CH3. ( 2 Marks )

(Q.171) Write the Finkelstein reaction. ( 2 Marks )

(Q.172) Complete the following reactions:
(a) C6H5ONa + C2H5Cl --------à
(b) CH3CH2CH2OH + SOCl2 ------>

(Q.173) p-dichlorobenzene has higher melting point and lower solubility than o- and m-isomer. Explain? ( 2 Marks )

(Q.174) How will you bring about the following conversions?
(a) Ethane to bromoethane
(b) 1-Chlorobutane to n-octane ( 2 Marks )

(Q.175) Identify chiral and achiral molecules in each of the following pair of compounds. ( 2 Marks )

(Q.176) Haloalkanes react with aqueous KOH to form alcohols but react with alcoholic KOH to form alkenes. Why? ( 2 Marks )

(Q.177) Write the Sandmeyer reaction. ( 2 Marks )

(Q.178) How will you prepare DDT? ( 2 Marks )

(Q.179) Identify the A and B in following reaction: ( 2 Marks )

(Q.180) Write the mechanism of the following reaction:( 2 Marks )
nBuBr + KCN nBuCN

(Q.181) Explain why alkyl halides are generally not prepared in the laboratory by free radical halogenation of alkanes. ( 2 Marks )

(Q.182) CHF3 is less acidic than CHCl3. Why? ( 2 Marks )

(Q.183) How the following conversions can be carried out?
(a) 1-Bromopropane to 2-bromopropane
(b) Aniline to chlorobenzene
(c) Benzene to diphenyl ( 3 Marks )

(Q.184) Haloalkanes undergo nucleophilic substitutions whereas haloarenes undergo electrophilic substitutions. Why? ( 3 Marks )

(Q.185) Explain why?
(a) Alkyl halides, though polar, are immiscible with water.
(b) Grignard reagents should be prepared under anhydrous conditions? ( 3 Marks )

(Q.186) Write the following name reactions.
(a) Friedal-Crafts acylation.
(b) Friedal-Crafts alkylation.
(c) Wurtz-Fittig reaction. ( 3 Marks )

(Q.187) Write the following name reactions.
(a) Gattermann reaction.
(b) Balz-Schiemann reaction.
(c) Hunsdiecker reaction..

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